mcverter: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On Debian possible default full paths are:

/usr/bin/mcverter - from package: mriconvert

You may install the required package with command apt-get install {package}

Error in other languages:
mcverter: bevel nie gevind nie
mcverter: comandă negăsită
mcverter: comando não encontrado
mcverter: commande introuvable
mcverter: command not found
mcverter: käsku ei ole
mcverter: không tìm thấy lệnh
mcverter: komanda nerasta
mcverter: Kommando nicht gefunden.
mcverter: kommandot finns inte
mcverter: komut yok
mcverter: nie znaleziono polecenia
mcverter: níor aimsíodh an t-ordú
mcverter: no se encontró la orden
mcverter: no s'ha trobat l'ordre
mcverter: opdracht niet gevonden
mcverter: parancs nem található
mcverter: perintah tidak ditemukan
mcverter: príkaz nenájdený
mcverter: příkaz nenalezen
mcverter: команда не найдена
mcverter: командата не е открита
mcverter: 命令找不到
mcverter: コマンドが見つかりません